1. Technical Field
The present invention relates to a printing device such as an inkjet printing device, a printing device control program, a printing device control method, a printing data producing device, a printing data producing program, a printing data producing method, a correction information producing method, and correction information producing device. The invention more particularly relates to a printing device, a printing device control program, a printing device control method, a printing data producing device, a printing data producing program, a printing data producing method, a correction information producing method, and a correction information producing device that are suitable for reducing degradation in printing quality caused by density variations attributable to the printing head.
2. Related Art
It has been difficult to manufacture printing elements such as nozzles for an inkjet printing device and heating elements for a sublimation type printing device with equal precision, and therefore the printing elements have unequal characteristics. The characteristics variations cause the amount of ink discharged from the nozzles and the ink arriving positions to vary, which generates so-called density variations including high and low density parts in a resulting printed image such as an image originally intended to be a solid image with equal density.
For example, JP-A-1-129667 and JP-A-3-162977 disclose an image forming device and an image recording device respectively as techniques for correcting the density variations and improving the printing quality.
The image forming device disclosed by JP-A-1-129667 corrects image data based on a density variation correction table in order to address density variations by a printing element.
The image recording device disclosed by JP-A-3-162977 corrects image data based on a density variation correction table in order to address density variations by a printing element, and also corrects image data based on a gradation correction table for each prescribed unit (each printing element at least), so that density variations in any gradation ranges can be restricted.
However, in the disclosure of JP-A-1-129667 and JP-A-3-162977, the correction is carried out so that the density variation characteristics of dots formed by the printing elements in each printing head attain a flat state. More specifically, the correction is carried out in order to prevent density variations by each printing head, and therefore at a joining part between printing heads in a multi-head type printing device, in particular, the flat characteristics are joined with each other, so that the density changes in a stepped manner as shown in FIG. 14 in the event that the characteristics are even slightly shifted from each other. At such a joining part, the density variations in the printing result are more noticeable than restricted.